Fluid property measurement devices, methods, and systems

ABSTRACT

High accuracy temperature measurement devices, methods, and systems for measuring the temperature of medical fluids are described. In embodiments, the devices have the features that they are compatible with the measurement of temperatures in a sealed fluid circuit, thereby promoting compatibility with sterile disposable circuits. Also described are combinations of temperature sensors and conductivity measurement for precise determination of the concentration of ions in a medicament.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.1/675,485, filed Jul. 25, 2012, the content of which is herebyincorporated by reference in its entirety.

BACKGROUND

The measurement of temperatures in medical devices can pose challenges.Many medical fluid flow paths are sealed and sterile, making itchallenging to introduce wetted temperature sensors into the flowwithout risking contamination. In addition, fluid circuits for infusiblefluids, medicaments, and biological fluids such as blood and plasma, areoften provided in the form of disposable components, making it importantfor temperature measurement strategies to be compatible with low cost ofsuch disposable components. Also, flowing blood poses a risk of formingclots when exposed to most materials and when flow paths are not smoothand conducive to non-turbulent flow, posing a challenging designconstraint for sensors. Still another challenge is the need fortemperature sensors in medical applications to provide high accuracy inmedical applications, for diagnostic purposes, for example.

SUMMARY

High accuracy temperature measurement devices, methods, and systems formeasuring the temperature of medical fluids are described. Inembodiments, the devices have the features that they are compatible withthe measurement of temperatures in a sealed fluid circuit, therebypromoting compatibility with sterile disposable circuits. Also describedare combinations of temperature detectors, which may be activetemperature detectors, and conductivity measurement for precisedetermination of the concentration of ions in a medicament.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an active temperature detector andsystem for measuring the temperature of a fluid in a vessel/channel orchannel, according to embodiments of the disclosed subject matter.

FIG. 2 shows a temperature distribution in a solid containingtemperature sensors for discussion of features of the disclosed subjectmatter.

FIG. 3 is a three-dimension view of a temperature profile along two axesfor discussion of features of the disclosed subject matter.

FIG. 4 shows a time profile of temperature error for a control scenarioembodiment where the difference between two temperature sensors in asymmetrical arrangement is used as the control input, according toembodiments of the disclosed subject matter.

FIG. 5 illustrates a device with an integrated temperature sensor thatincludes an active temperature detector according to any of theembodiments of the disclosed subject matter.

FIG. 6 shows a disposable active temperature detector, according toembodiments of the disclosed subject matter.

FIGS. 7A and 7B illustrate active temperature detector embodiments thatemploy a temperature controlled surface, which may be provided by asurface of an actively controlled heating/cooling device, according toembodiments of the disclosed subject matter.

FIG. 7C shows a table that identifies mechanisms for obtaining a fluidtemperature estimate from the embodiments of FIGS. 7A and 7B, accordingto embodiments of the disclosed subject matter.

FIGS. 8A and 8B illustrate method and structural aspects of aconductivity measurement scheme, according to embodiments of thedisclosed subject matter.

FIG. 9A shows a conductivity measurement device with a controller, anactive temperature detector and a conductivity/temperature measurementcell in a module which may form a disposable component, in a firstconfiguration prior to use, according to embodiments of the disclosedsubject matter.

FIG. 9B shows a conductivity measurement device with a controller, anactive temperature detector and a conductivity/temperature measurementcell in a module which may form a disposable component, in a secondconfiguration adapted for use, according to embodiments of the disclosedsubject matter.

FIG. 9C shows a variation of the embodiment of FIGS. 9A and 9B in whichelements for making two temperature measurements, one before aconductivity cell, and one after, according to embodiments of thedisclosed subject matter.

FIG. 10A shows a conductivity measurement device with a temperaturemeasurement portion and a conductivity measurement portion, according toembodiments of the disclosed subject matter.

FIG. 10B shows details of a fluid channel portion which may form part ofa disposable circuit, according to embodiments of the disclosed subjectmatter.

FIG. 11A shows a first view of an active temperature detector permanentpart that is used for measuring temperature inside of a vessel/channelor channel, according to embodiments of the disclosed subject matter.

FIG. 11B shows further aspects of the active temperature detectorpermanent part of FIG. 11A, according to embodiments of the disclosedsubject matter.

FIG. 11C shows further aspects, in section, of the active temperaturedetector permanent part of FIG. 11A, according to embodiments of thedisclosed subject matter.

FIGS. 11D and 11E show wiring and structural features that may be usedwith various embodiments, for example, the active temperature detectorpermanent part of FIG. 11A, according to embodiments of the disclosedsubject matter.

FIG. 11F shows a variant of the embodiment of FIGS. 11D, 11E, accordingto embodiments of the disclosed subject matter.

FIG. 10B shows details of a fluid channel portion which may form part ofa disposable circuit, according to embodiments of the disclosed subjectmatter.

FIG. 12 a cross-section of an embodiment that includes all heat transferand sensor aspects of a temperature measurement device according toembodiments of the disclosed subject matter.

FIG. 13 shows a method for verifying thermal contact between an activetemperature detector and a wall of a fluid vessel/channel according toembodiments of the disclosed subject matter.

FIG. 14 shows an active temperature detector with features for verifyingthermal contact between a surface thereof and a wall of a fluidvessel/channel according to embodiments of the disclosed subject matter.

DETAILED DESCRIPTION OF THE DRAWINGS AND EMBODIMENTS

Embodiments will hereinafter be described in detail below with referenceto the accompanying drawings, wherein like reference numerals representlike elements. The accompanying drawings have not necessarily been drawnto scale. Where applicable, some features may not be illustrated toassist in the description of underlying features.

The disclosed subject matter provides a mechanism, device, system, andmethod for accurately measuring a fluid temperature inside a vessel. Theterm vessel/channel for purposes of the invention may encompass anyfluid containing device including one that conveys fluid in a continuousor intermittent flow, or storage container. Fluid vessels may includecontainers and fluid conveyances such as flexible wall bags, panel-typeflow through channels, or tubes. According to embodiments, the disclosedsubject matter may be used for measuring the temperature of fluidcontained by a vessel/channel having a wall having any properties, butfinds particularly merit in applications where the wall presents asubstantial thermal resistance between the fluid and the temperaturesensor, such as when a temperature sensor is located outside thevessel/channel wall.

A feature of the disclosed devices and methods is the substantialnegation of heat flow between the fluid and the sensor that canotherwise occur due to any difference in temperature between the ambientenvironment outside the vessel/channel and the fluid.

Active temperature compensation according to the disclosed embodimentsmay improve the fluid temperature sensing accuracy and may also reducethe measurement response time.

In embodiments of the disclosed subject matter, one or more temperaturesensors such as thermistors, thermocouples, RTD, quartz thermometers,etc., are placed against a surface of a fluid vessel/channel or channelsuch that the temperature sensor is separated by a wall of the fluidvessel. To illustrate the operation of the active temperature detector,the operation of this configuration is now discussed in the absence ofactive temperature compensation.

A side of the temperature sensor opposite the vessel/channel wall isadjacent an external environment which is, at least at certain times, ata different temperature from that of the fluid so that heat is conductedfrom, or to, the fluid and the external environment. The wall and thepath to the external environment represent thermal resistance to heatflow through the vessel/channel wall. The thermal resistance can besubstantial for vessels with low conductivity such as plastic vessels.The resistance in the heat flow places the temperature sensor at atemperature intermediate between that of the fluid and that of theexternal environment.

The thermal properties of the vessel/channel wall can also result inundesirable transient effects. The thermal properties of the wallinclude thermal capacitance as well as conductivity and the ratio of thewall's conductivity to capacitance, i.e., the thermal diffusivity,determines the responsiveness, or settling time, of the fluid-sidetemperature sensor measurement. Long settling times can lead toinaccurate temperature indications when the fluid temperature changesrapidly.

For such a passive temperature sensor configuration, the error intemperature indication of an uncompensated sensor can be calculated asfollows. If R_(a) =Thermal resistance between sensor and ambient;R_(w)=Thermal resistance between sensor and fluid through thevessel/channel wall (bag); T_(f) is the fluid temperature and T_(a) isthe ambient temperature, then the sensor temperature error T_(e) atequilibrium will be T_(e)=(T_(f)−T_(a))*[R_(f)/(R_(f)+R_(a))].

This calculation is simplified and assumes the system can be modeled asa simple thermal network. The inherent approximations relative to thereal world should be evident from the foregoing discussion. In addition,the transient response of the system which is not described in furtherdetail is more complex, but is also addressed by active temperaturedetectors according to the disclosed embodiments.

The disclosed subject matter includes embodiments of an active sensordevice that combines a fluid-side temperature sensor with aheating/cooling device (for example a thermoelectric device) and a heatflow sensor. In all of the embodiments, a heating/cooling device(meaning a heating or cooling device or one capable of heating orcooling) is incorporated in apparatus defining a thermal network thatincludes at least one temperature sensor and preferably two. The deviceis placed in thermal contact with the wall of a vessel/channel orchannel containing a fluid whose temperature is to be measured. Thethermal network is any kind of components that can transfer heat betweenthe wall and the heating/cooling device and which network can be allow acontroller to calculate the fluid temperature from the indicatedtemperature of the at least one temperature sensor and/or regulate theheating/cooling device so as to halt any thermal gradient in the thermalnetwork such that the temperature of the at least one temperature sensormust be equal, in the steady state, to the fluid temperature. Inembodiments where two temperature sensors are used, one may bedistinguished from the other by being closer to the fluid and the othercloser to the heating/cooling device.

Referring to FIG. 1, an active temperature detector 100 has a fluid-sidetemperature sensor 112 positioned adjacent the wall 106 of a vessel. Aheating/cooling device 102 is positioned on a side of the fluid-sidetemperature sensor 112 opposite the fluid vessel/channel wall. Note thatin the present disclosure, in any of the embodiments in a wallseparating the active temperature detector and the fluid may be that ofa vessel, container, a flow path, a fluid circuit element or any otherfluid containing or carrying device. The heating/cooling device 102generates heating or cooling effect that is regulated to maintain atemperature of the fluid-side temperature sensor 112, on a side oppositethe vessel/channel wall, at substantially the same temperature as thatof the fluid such that there is, substantially, no heat flow through thevessel/channel wall 106. To provide the control of the heating/coolingdevice 102, the active sensor device further includes a controlcomponent that generates a control signal that indicates a temperaturedifference to be minimized or a thermal flux measurement.

The control component, in the present embodiment, includes anheating/cooling side temperature sensor 110 and a controller 120, whichmay have a user interface for receiving commands and outputting data.The heating/cooling side temperature sensor 110 is separated from thefluid-side temperature sensor 112 by a material that provides a thermalresistance, in the example an insulator 104 that may be formed frompotting material (e.g., epoxy, thermoplastic, laminated glass epoxy)that supports the components and forms an integrated device with uniformthermal contact between components. In the present embodiment, thecontroller 120 receives signals from the fluid-side temperature sensor112 and the heating/cooling side temperature sensor and generates anerror signal responsively to them, for example, the error signal may bea difference between the temperature indications of the fluid andheating/cooling side temperature sensors 112 and 110. The controller 120uses the error signal to regulate the heating/cooling device so as tominimize the difference between the temperature indications of theheating/cooling side temperature sensor 110 and the fluid-sidetemperature sensor 112. For a physically wide active temperaturedetector (width being indicated by arrows 123 and the direction normalto the page), heat flow is substantially entirely limited to flow in thedirection joining the fluid and heating/cooling side temperaturesensors. Thus, the above-described error signal is effectively anindication of all heat flow through the vessel/channel wall 106. Becausethis heat flow is negated by the control of the heating/cooling device102, then the fluid and heating/cooling side temperature sensors 112 and110 will both indicate the fluid temperature. The fluid temperaturesignal indicated by the device 100 may be taken from the fluid andheating/cooling side temperature sensors 112 and 110 or an average ofboth.

In the embodiment 100, the thermal resistance of the insulator 104 maybe selected to be comparable to that of the vessel/channel wall, higher,or lower. For temperature measurements where slow transient response isacceptable, a material with a low conductivity, with a concomitantly lowthermal diffusivity, will provide an error signal (based on theindicated temperature difference of the ambient-side and fluid-sidetemperature sensors 110 and 112) whose magnitude is greater for a givenheat flux. This may improve temperature measurement precision. Fortemperature measurements where faster transient response is required, amaterial with a higher conductivity and a concomitantly high thermaldiffusivity, will provide a smaller error signal for a given heat flux,but will provide shorter settling time and thereby “follow” a variablefluid temperature more accurately.

The thermoelectric device generates a heat or cooling effect at a ratecontrolled to maintain a surface such that surface of the thermoelectricdevice that faces the sensor is controlled such that its temperature isequal to the fluid temperature. In this case T_(a)=T_(f)=T_(s) and themeasurement error approaches zero. For cooling effect, an active heatpump may be used, for example a thermoelectric heat pump may be used.For measurement of temperatures that are above ambient, theheating/cooling device may be a heater that provides cooling effect bymeans of heat transfer to the surrounding environment.

To enhance the heat transfer from the insulator 104, vessel/channel wall106, and temperature sensors 110 and 112, a heat sink may be employed onthe heating/cooling device 102. In a heating/cooling device that issimply a dissipative heater (such as an electrical resistance heater),the heat sink may provide passive cooling through the dissipative heaterto the ambient environment. Thus, for effective transient operation,heat stored in the insulator 104 and other components may be rejected toallow for equilibration of the temperature sensors when a negative-goingchange in fluid temperature occurs. This may be provided by ensuringthat the electrically dissipative heater transfers heat effectively tothe heat sink 101. An active heating/cooling device such as a thermopilewill employ a heat sink of some type but may actively pump heat to/fromthe heat sink and the insulator 104 and other components. For mostapplications it may be desirable to employ an electrically dissipativeheater (resistive or semiconductor) or thermoelectric device for theheating cooling device 102, however, the heating cooling device 102(including heat sink 101) may be replaced with an active heating coolingdevice employing a mechanical system such as a container whose internaltemperature is thermostatically regulated.

In embodiments, the controller 120 may include a feedback controlcircuit that regulates current to the heating/cooling device 102, whichmay be, for example, a thermoelectric heat pump (e.g., thermopile) ordissipative heater. The current may be supplied and controlled usinglinear or switching power technology. The controller 120 regulates thetemperature of the heating/cooling device 102 so that the temperatureindicated by the heating/cooling side temperature sensor 110 is equalto, or transiently approaches, the temperature indicated by thefluid-side temperature sensor 112. When these two temperatures areequal, there is no net heat flow between them. Because effectively allheat that flows between the two sensors also flows between thefluid-side temperature sensor 112 and the heating/cooling sidetemperature sensor 110.

According to the foregoing embodiments, a temperature sensing error thatresults due to heat flowing from a fluid to the ambient environmentthrough the vessel/channel wall 106 is minimized. The heat flow throughthe vessel/channel wall 106 is primarily normal through the wall, butsome heat flow through the ends 122 of the insulator 104 occurs. Theisothermal environment is provided for the fluid-side temperature sensor112 using active control as described. The heating/cooling device 102may have a surface 130 of a low thermal resistance material such asAluminum Nitride ceramic to ensure a uniform temperature of the surfaceinterfacing the insulator 104 is provided. The size of the sensorsurface 130 may be made much larger than the size of the sensor 112 andthe thickness of the insulator 104 may be made low such that thetemperature of the insulation 104 and vessel/channel wall 106 near thesensor 112 to reduce thermal storage in the insulator 104 and decreaseheat transfer from the ends 122 and thereby maintain the temperature ofthe fluid-side temperature sensor very close to the temperature of theheating/cooling device 102 surface 130.

A heat sink 101 may or may not be provided depending on the propertiesof the system and/or the type of thermoelectric device. For example, inan embodiment with a low aspect ratio and high heat flow from the ends130 may not require a separate heat sink 101. The control systemparameters may be chosen to allow the temperature indicated byfluid-side temperature sensor 112 to track closely the temperature ofthe target fluid 116. In embodiments, the controller 102 may employproportional—integral—derivative controller (PID controller) orfeed-forward control features. A feed-forward controller may employ aninternal model and fit two or more spaced temperature measurementswithin the insulator 104 to a predictor of the fluid temperature to morerapidly adjust the heating/cooling device 102 temperature.

The active sensor device 100 reduces the response time of the thermalmeasurement. The relatively high heat flow provided by theheating/cooling device in combination with a high controller gain mayprovide higher thermal gradients in the sensor, as compared to a passivesensor, which drive the sensor temperature to settle to its final valuefaster.

Some details of background technology for temperature sensors aredescribed in U.S. Pat. Nos. 3,933,045 and 4,968,151, which areincorporated by reference in their entireties herein.

In alternative embodiments, the device that generates an indication ofheat flux may include an heating/cooling side temperature sensorseparated from the fluid-side temperature sensor with a material betweenthem that provides thermal resistance as described with reference toFIG. 1. Alternative embodiments may employ a separate heat flux sensor.For example, a heat flux sensor may be attached to the ambient-facingside of the fluid-side temperature sensor 112, taking the place of theinsulator and heating/cooling side temperature sensor. In yet anotheralternative embodiment, a flux sensor may be combined with the activetemperature detector device 100 of FIG. 1 and located at an intermediateposition within the insulator 104. As mentioned, in still otherembodiments, temperature sensors may be located at multiple positionswithin the insulator 104 and used to estimate of net heat flow throughthe vessel/channel wall 106 which is then used as the control input forthe controller. In embodiments, the multiple temperature indications maybe combined to reduce random error or combined and used for feed-forwardcontrol as mentioned.

In a particular alternative embodiment, in contrast to embodiment 100where the heating/cooling side temperature sensor 110 is locateddirectly adjacent the heating/cooling device 102, an heating/coolingside temperature sensor may be positioned intermediate between theheating/cooling device 102 and the fluid-side temperature sensor 112.For example, a heating/cooling side temperature sensor may be separatedfrom the heating/cooling device 102 by an ambient-side insulator thathas the same or similar dimensions and thermal properties as that of thevessel/channel wall 106. In FIG. 2, a curve 209 indicates a temperatureprofile between the heating/cooling device at 201 and the fluid at 203.The vessel/channel wall spans the gap 208 and the ambient-side insulatorspans the gap 206. The arched temperature profile arises due to a smallheat flow from the ends (indicated at 122) of the active temperaturedetector 100 as modified according the present embodiment. Thetemperature indicated by the fluid-side temperature sensor is shown at204 and the temperature indicated by the heating/cooling sidetemperature sensor is shown at 202. Because of the symmetricalarrangement, the minimization of the difference between the fluid andambient side temperature indications 202 and 204 drives the temperatureof the heating/cooling device interface 201 toward the fluid temperature203.

In any of the disclosed embodiments, the temperature sensor closest tothe fluid vessel/channel may be separated therefrom by additionalelements such as adhesive, thermal paste, or structural members. Thedisclosed embodiments may be applied to applications for the measurementof temperatures of fluids and other materials including solids, gas,liquid, and multiphase fluids.

A pump 133 that regulates a rate of flow of fluid 116 through a fluidcircuit partly enclosed by the wall 106. The fluid circuit may be anytype of fluid circuit. The circuit may have flat portions such asexpanded elements of a circuit defined between parallel panels that aremolded or seam welded to define flow paths between them. The controller120 may be configured to activate the heating/cooling device 102 onlywhen a flow of a predefined magnitude is established so as to avoid therisk of causing heat buildup in the fluid 116 or erroneous temperaturemeasurements. The predefined flow may be established by regulation ofthe pump 133. In an embodiment, the controller 120 only permits theheating/cooling device 102 to activate, and temperature samples to beacquired, when the pump is operated at a predefined minimum speed.

Referring now also to FIG. 3, a surface plot 240 shows the temperaturedistribution at steady state including the vessel/channel wall 106 (edge244 coinciding with the fluid) and the insulator 104 with the fluid 116and heating/cooling device 102 (boundary of heating/cooling device 102is indicated at 246) providing boundary conditions as well as edges 242.The plot shows the temperature distribution for a device with an aspectratio of 4.5 (width 123 to thickness 125). The insulator simulated hadthe same properties as the fluid vessel/channel wall and it was assumedthere was not separate contact resistance at the interface of thevessel/channel wall with the insulator. It may be seen that despite thelow aspect ratio of 4.5, the temperature profile along the middle shownin FIG. 2 only deviates by 0.3% of the temperature difference betweenthe fluid 32C and the ambient 20C. Also, when the temperature of theheating/cooling device interface 201 is used as the indicator of fluidtemperature, the deviation is lower. FIG. 4 shows a time profile oftemperature error for the control scenario discussed above where thedifference between the two temperature sensors in the symmetricalarrangement discussed with reference to FIG. 2 is used as the controlinput. That is, the controller minimizes the difference between thefluid and ambient side temperature indications 202 and 204, to drive thetemperature of the heating/cooling device interface 201 toward the fluidtemperature 203. The reference numeral 360 indicates the absolute valueof the difference between sensors at 202 and 204 as described withreference to FIG. 2. It can be seen with simple proportional controlthat the system settles to near zero error within 2 seconds after aninstantaneous fluid temperature change of 2C. For this simulation, itwas assumed that the heater response was immediate with a simpleproportional control.

FIG. 5 illustrates a device 302 with an integrated temperature sensorthat includes an active temperature detector device 312 according to anyselected one of the foregoing embodiments. The active temperaturedetector device 312 has a contact temperature sensor 314 with a surfaceconfigured to make thermal contact with a vessel/channel 306 integratedin an installable component 308 which is attached by way of anattachment mechanism 310 to the device 302. The vessel/channel 306 maybe a panel shaped fluid circuit component or a flexible-walled containerand the component 308 may be a fluid circuit, for example, oneinstallable on a medical treatment device. The device 302 may be amedical treatment device, for example, a dialyzer. The active sensordevice 312 further includes a contact portion 313 that provides the sameheat transfer properties as the contact temperature sensor 314. Aheating cooling device and an ambient side temperature sensor (notshown) as well as other elements behind the contact temperature sensor314 and contact portion 313 operate as described above to measure thetemperature inside the vessel/channel 306. A movable component 316 maybe closed over the component 308 and configured to hold thevessel/channel 306 against the combined surface of the temperaturesensor 314 and contact portion 313. In embodiments, the activetemperature detector device may be integrated in a bag support in whichthe weight of fluid in the bag holds the wall of the bag against thetemperature detector 314 and contact portion 313 or in which pumpingpressure is used. The device 302 may include controller components.

FIG. 6 is a disposable version of an active temperature detector. FIG. 6illustrates a fluid vessel/channel 450 with a temperature measurementcomponent 405 and a complementary measurement device 401. Thetemperature measurement component 405 may incorporate a series oflayered components including a fluid-side temperature sensor 414 and anheating/cooling side temperature sensor 424 separated by a thermallyinsulting film 413. In an alternative embodiment, the heating/coolingside temperature sensor is included in component 450 and not a part ofthe temperature measurement component 405. An electrically dissipativeheater 426 may be attached to the above opposite a wall 400 of a fluidcontainer 450. An insulating layer may be positioned between theelectrically dissipative heater 426 and the heating/cooling sidetemperature sensor 424 to provide a symmetric arrangement as discussedabove with reference to FIG. 2. Electrical contacts 428 may be connectedto the sensors 414 and 424 and to the current leads of the electricallydissipative heater 426 and arranged to mate with complementaryconnectors 448 on the complementary measurement device 401. A controller446 and interface component 442 may be provided as part of thecomplementary measurement device 401 and forming a permanent fixture.The temperature measurement component 405 and container 450 may beconfigured as a disposable component, for example a flexible walled bagwith the temperature measurement component being a laminated structurethat is thermally welded or adhesively bonded thereto. In an alternativeembodiment, an electrically dissipative heater 448 is incorporated inthe permanent complementary measurement device. In this embodiment, thecontacts 428 and 448 would not include current contacts for a heaterintegrated in temperature measurement component 405.

Referring now to FIGS. 7A and 7B, in alternative embodiments, an activetemperature detector employs a temperature controlled surface 502, whichmay be provided by a surface of an actively controlled heating/coolingdevice such as described with reference to the foregoing embodiments. Acontainer wall 504 separates a fluid 520 from a temperature sensor 510.Temperature sensor 510 and additional sensors 506 and 508 within aninsulating body 512 (which may be formed of one or more layers that arenot shown). In another embodiment, multiple sensors 526 lie within theinsulating body 512.

Referring to FIG. 7C, a table 550 identifies four mechanisms (552, 554,556, and 558) for obtaining a fluid temperature estimate from theembodiments of FIGS. 7A and 7B. The first column 560 identifies theerror signal for feedback control of the temperature of the temperaturecontrolled surface 502. The second column 562 identifies the indicatorof the fluid temperature, which is the temperature of the fluid 520whose magnitude is indirectly measured by the embodiments.

In embodiment 552, the error signal is the difference between atemperature of the temperature controlled surface 502, or a temperatureof the insulator 512 close to the temperature controlled surface 502(indicated at 506), and a temperature of the vessel/channel wall 504, ora temperature of the insulator 512 close to the vessel/channel wall 504(indicated at 510). In any case, 506 indicates a temperature sensor thatindicates substantially the temperature T_(a) of the temperaturecontrolled surface 502 and 510 indicates a temperature sensor thatindicates substantially the temperature T_(f) of the vessel/channel wall520. The difference T_(f)−T_(a) is applied as an input to the controllerto raise or lower the temperature of the temperature controlled surface502. In the present or any of the embodiments, the controller (not shownin the present figures but as described earlier) may employ anyappropriate control algorithm or apparatus, for example, a proportional,integral, differential control scheme, proportional differential controlscheme, proportional, integral; integral; or simple proportional controlscheme. Another simple alternative is simple limit cycle control such asused in thermostats. The controller also may employ open loop controlusing the error or the individual inputs themselves to predict thetemperature error and regulate T_(a) accordingly. In embodiment 552, theoutput indicating fluid temperature may be T_(a), T_(f) or sometemperature T_(i) at indicated by a sensor 508 located at anintermediate point in the insulator 512. Note that variations of theembodiment 552 can be formed by using intermediate temperatures such asTi as part of the error signal (e.g., T_(a)−T, T_(s)−T_(f) or twointermediate temperatures) where any two intermediate temperaturesensors at different locations in the insulator are used to indicate aheat flow between the surface 502 and the fluid.

Embodiment 554 is an example where an error T_(f)−T_(i) is used forcontrol of the temperature controlled surface 502, T_(f) and T_(i) areindicated by the intermediate sensor 508 and sensor 510 and in whichsensor 508 is positioned so that the thermal resistance between it andthe temperature controlled surface 502 is substantially the same as theresistance between sensor 510 and the fluid 520. In embodiment 554, theoutput indicating fluid temperature may be T_(a), T_(f), or T_(i).

In embodiment 556, multiple temperature sensors 526 located in theinsulator 512 indicate temperatures T_(j) at various positions in theinsulator 512, thus indicating a temperature profile there within. Inthis embodiment, the temperature controlled surface 502 may be regulatedto hold a constant temperature. As the temperature of the fluid 520changes, temperature disturbances pass through the vessel/channel wall504 and into the insulator 512 changing the temperature profileindicated by temperatures T_(j). A controller may employ a processor toform a curve to the temperature profile T_(j) and then use a pointextrapolated therefrom as an indication of the fluid temperature. Inother words, the temperature profile at any given time is given by thefitted curve and includes, by extrapolation, the temperature of theinterior surface 521 of the vessel/channel wall 520. This computedtemperature may be output by the controller as the fluid temperature. Ina variation, indicated by embodiment 558, employs an internal model ofthe thermal system including the insulator 512, the vessel/channel wall504, and if desired, other features such as the film coefficient at thesurface 521. In this embodiment, the model is fitted to the measureddata points T_(j) and the fluid temperature estimated from the model'srepresentation of the fluid temperature.

Although in the foregoing embodiments, a member lying between thevessel/channel wall and the heating/cooling device (or schematically,the temperature controlled surface 502) is identified as an insulator,this is not intended to indicate a limited range of materials. Materialswith any suitable combination of thermal capacitance and conductivitywill possess some degree of resistance to heat flow and thereby fallwithin the term insulator. In addition, the insulator may or may notinclude multiple layers or otherwise form a composite structure. Theinsulator may incorporate cooling features such as layers of highconductivity material to promote the transfer of heat in specificdirections, for example. In specific embodiments it may be desirable tochoose an insulator material or materials whose thermal properties areclose to those of the vessel/channel wall.

Other variations of the foregoing embodiments include ones in whichinstead of a vessel/channel wall lying between the active temperaturedetector and a target substance, some other thermal resistance ispresent, for example, a material overlying a solid body whosetemperature is desired to be measured. Also, as mentioned above, insteadof additional temperature sensors being embedded in an insulator, aseparate thermal flux transducer may be employed.

Referring now to FIGS. 8A and 8B, a conductivity measurement device 580has a continuous flow path 592 leading to a first temperaturemeasurement cell 582, then to a conductivity measurement cell 584, andthen to a second temperature measurement cell 586. The first and secondtemperature measurement cells provide temperature measurement readingsof the fluid temperature flowing through the continuous flow path 592.The temperature reading provided by the first measurement cell 582 maybe combined with those from the second measurement cell to generate astatistic representing the temperature of the fluid at the point whereits conductivity is measured by the conductivity measurement cell. Forexample, the two temperature measurements may be averaged over a timeinterval during which the fluid flows at a constant rate. During thistime interval, the conductivity of the fluid flowing through theconductivity cell may be measured using a wetted electrode resistancemeasurement through a fixed length of the flow path. The process takesplace while a continuous flow exists in the flow path 592. A controller594 may receive the temperature and conductivity measurements and detectthe conditions for sampling and storing measurement data, deriving astatistic therefrom, and calculating the fluid properties from thestatistic. A single temperature sensor may be used as well. The singlesensor embodiments, may advantageously locate the single sensor close tothe fluid. Any of the embodiments may be modified to use a singletemperature sensor. In all of these, the temperature sensor may belocated adjacent to, or close to the fluid.

The above measurement process using the system 580 is now described withreference to FIG. 8A. Fluid is pumped through the conductivity andmeasurement cells at S100. While the fluid is flowing, one or moretransient variables are monitored until an equilibrium condition isestablished. The equilibrium condition may coincide with, for example,an unchanging temperature, an unchanging raw conduction measurementindication, an unchanging flow rate, or with an unchanging fluxmeasurement for the active temperature detector device described above,if used for temperature measurement. Once the equilibrium condition isdetected at S104, samples of conductivity and temperature are obtainedand stored at S106. The sample data may be tested against predefinedlimits to ensure the sampled data are valid and if they pass, at S108,representative statistics may be derived at S110. Fluid parameters suchas salinity, concentration, species molarity, or other parameters ofinterest may be generated by correlation of the raw conduction orconductivity measurement and temperature statistic with the parameter ofinterest at S114. The fluid temperature is measured to compensate theconductivity measurement to allow for accurate determination of a fluidproperty, such as ion concentration or standardized conductivity (e.g.,referred to a standard temperature such as 25 C). This may be doneinternally by a controller and operations of a fluid handling device maybe automatically governed by the outcome. For example, a fluid handlingsystem may alert an operator to an improper fluid property determinationor it may shut down an operation such as a treatment showing an improperconcentration of a medicament. A variety of different operating regimesmay be responsive to an output of the property measurement anddetermination disclosed herein.

Referring now to FIG. 9A, a conductivity measurement device 600A has acontroller 602, an active temperature detector 604 (together forming ameasurement component 601A) and a conductivity/temperature measurementcell 610 in a module 606 (which may form a disposable component). Afluid line 601 carries fluid into the conductivity/temperaturemeasurement cell 610. A pair of conductors 611 in the cell connected toa driver circuit (current source and voltage measurement circuits) inthe controller to measure the fluid conductance in the fluid columnbetween the conductors 611. An insulator 608 with temperature sensors, aheating/cooling device 609, and the controller 602 may be configured asdescribed according to any of the embodiments described herein tomeasure the temperature of fluid in the conductivity/temperaturemeasurement cell 610. The module 606 has an urging mechanism 612 thaturges the conductivity/temperature measurement cell 610 against theinsulator 608 to ensure good and uniform contact between the planar areaof the conductivity/temperature measurement cell 610 and the insulator608. At the same time, the urging mechanism may also mate, and ensuregood electrical contact, between electrical contacts that connect theconductors 611 to contacts of a driver circuit within the controller602. A support aligns and supports the module 606 and provides a basefor urging mechanism 612. FIG. 9A shows the permanent component 601Aprior to connection to the measurement component 601A and FIG. 9B afterconnection.

FIG. 9C shows a variation of the embodiment of FIGS. 9A and 9B in whichelements for making two temperature measurements, one before aconductivity cell 609, and one after. In the configuration of FIG. 9C,the module 607 combines two temperature measurement cells 617 with asingle conductivity measurement cell 609. Temperature measurements aremade prior to and following the conductance measurement and thetemperature measurements may be averaged to ensure a more accuratetemperature estimate during the conductance measurement in the event ofany temperature change a fluid flowing through the line 601 whileconductance is being measured. The elements labeled with like referencenumerals are as described with reference to FIGS. 9A and 9B. Each of theconductivity/temperature measurement cells 610 and temperaturemeasurement cells 617 may be of a somewhat flexible material which maybe pressurized to allow fluid to flow through the cell while being urgedagainst the insulator 608. Alternatively, each of theconductivity/temperature measurement cells 610 and temperaturemeasurement cells 617 may be of a rigid material and the insulator 608provided with a sufficiently compliant surface to ensure good anduniform thermal contact. In another variation, the latter embodiment mayemploy an intermediate material such as thermal grease or a thermal padsuch as used to join heat sinks to solid state circuit packaging inelectronic devices.

Referring to FIGS. 10A and 10B, FIG. 10A shows a conductivitymeasurement device 700 with a temperature measurement portion 704 and aconductivity measurement portion 702 that engage, by closingtherearound, a disposable conductivity/temperature measurement cell 706(shown also in FIG. 10B). The insulators 708 and 711 of activetemperature detectors face, and contact, chambers 742 and 744. Thetemperature/conductivity measurement cell 706 engages with thetemperature measurement portion 704 and the conductivity measurementportion 702 when they two are brought together around the conductivitymeasurement cell 706. The conductivity measurement cell 706 has aconductivity measurement column 718 with wetted conductors 720 and 722which connect with contacts (not shown) in the conductivity measurementportion 702. A continuous flow path is defined between an inlet 736 andan outlet 738. The continuous flow path enters chamber 742 via elbow 714through a first opening 731 leaves the chamber 742 through a secondopening 732 leading to the conductivity measurement column 718 via elbow714. Fluid leaves the conductivity measurement column 718 via elbow 716and flows through opening 734 to pass into chamber 744 and then outthrough opening 735 where the flow exits through outlet 738. A pair ofparallel panels 725 is seam welded as indicated at 712 and 728 to formthe chambers 742 and 744. The panels are of material that provides somestiffness to support the conductivity measurement column 718 and theinlet 736 and 738 portions. The panels also provide sufficientflexibility to provide a conforming interface to the insulators 709 and711.

The temperature measurement portion 704 and conductivity measurementportion 702 contain respective measurement circuits as describedaccording to any of the disclosed embodiments. The temperaturemeasurement portion 704 and conductivity measurement portion 702 closearound, and engage, the conductivity measurement cell 706 to makethermal and electrical contact therewith. The conductivity measurementcell 706 may be permanently affixed to a fluid circuit, such as amedical treatment disposable circuit, for example, one for hemodialysis,peritoneal dialysis, treatment fluid preparation systems, etc.Conductivity measurement may be used in such systems for fluid propertyverification, for feedback-based preparation of target formulations, orfor fluid property determination for any other purpose.

To make electrical contact between a conductivity measuring circuit andthe wetted conductors 720 and 722, spring loaded contacts may beemployed, one contacting each end of the electrode (each electrode 720and 722 has two exposed ends). By using two contacts, for example, pogopin type contacts, one at each end, a continuity test verifying contactwith each pin (the continuity being between a first contact with one endof an electrode 720 or 722 and a second contact with the opposite end ofthe electrode 720 or 722) may serve as an indication that the disposableconductivity/temperature measurement cell 706 is properly positioned foruse. The same continuity test can be done for both electrodes 720 and722 and a control system may verify both continuity paths to confirmcomplete connection. It is noted that a regulated current source may beemployed in conjunction with a high impedance voltage measurement devicewith the current applied at one end of each conductor and the voltagemeasurement made across the other end of each conductor. This isessentially a four-point conduction measurement which is not susceptibleto the error which may be introduced by contact resistance in thevoltage measurement. In this way, even if there is some contactresistance between the contacts and the electrodes 720 and 722, apredefined current will be established in the fluid column 718 of thecell whilst the high impedance voltage measurement will not be affectedby the contact resistance. Thus, measurements will be reliable andaccurate even in an instance where imperfect contact is made between themeasuring circuit and one or both of the electrodes 720 and 722. Also,having provided dual contacts at each end of the conductivity cellcolumn, the dual contacts are employed to determine, by continuitydetection, if the conductivity cell is properly loaded. If continuity isnot confirmed, an error signal may be generated and output by thesystem.

In additional system embodiments, the conductivity measurement may beused to verify the concentration of medicaments being supplied to atreatment system at the time of use. For example, at a time when atreatment system is being set-up, for example, a hemodialysis system,the dialysis fluid can flow into a conductivity detection systemaccording to the disclosed embodiments, and a conductivity measurementcompared to a prescription or other predefined indication of correctvalues or range of values. If the measurement fails to conform to thepredefined range, an output can be generated to indicate the failure.Since the present system is capable of measuring temperature accurately,the conductivity measurements can be very precise and therefore they mayindicate an attempt to use an incorrect prescription on a patient. Anintegrated system may also take automatic corrective action in responseto an output indicating incorrect conductivity or concentrationmeasurement.

In any of the embodiments, in addition to measuring conductance by meansof wetted electrodes, other types of conductance (equivalently,resistance or resistivity) measurements may be employed, includingcontactless measuring devices, for example, magnetic induction devicesmay be employed for conductance measurement. Also, conductivity can bemeasured by devices that employ capacitive coupling as a means formeasuring. Other specific technology for measuring conductance may alsobe employed.

An embodiment conforming to the general description of FIG. 5 andemploying features of FIGS. 9A through 10B (as well as any othersdisclosed that are compatible) is an online medicament (e.g., dialysate)preparation device. An online system may have a mixing portion where themixing ratios are continuously adjusted by a controller according to afeedback circuit providing conductivity measurement signal using theembodiments of FIGS. 9A through 10B and others. Such a system may have adisposable component to promote sterility and reduce the risk ofcontamination. A disposable component may have water filtration andmixing components in it. It may be desirable in such a system togenerate the conductivity signal from the devices disclosed herein whichprovide highly accurate conductivity and temperature data to allow theconcentration of medicament to be controlled, for example by feedbackcontrol. For example, the concentration of electrolytes in a medicamentcan be measured accurately with the conductivity and temperature signalprovided by the present system. The synergy arises here because theaccurate temperature measurement can be taken through the wall ofdisposable fluid circuit portion thereby to avoid the disruption of thecircuit's sterile isolation from the outside environment or theinclusion of expensive additional components such as wetted temperaturesensors. We note here that any of the features of the active temperaturedetectors may be incorporated in such a system as FIGS. 9A through 10Band others, such as those of FIGS. 11A through 14.

For example a system for generating a medicament may have a fluidcircuit with a disposable portion. The fluid circuit may include a fluidconduction measuring portion and a temperature detecting portion as inany of the disclosed embodiments herein. The fluid circuit may have amixing portion where the disposable portion is connected to convey amixed product flowing from the mixing portion. A temperature detectingdevice according to any of the embodiments (including any of the claims)may be provided to contact with the disposable portion and measure atemperature of a mixed fluid flowing therethrough and to output atemperature signal. The conduction measuring portion may be configuredto measure a conductivity of the mixed product flowing from the mixingportion and output a conductivity signal. A controller may be configuredto control a relative flow of water and a concentrate into the mixingportion responsively to both of said temperature and conductivitysignals. The controller may be configured for feedback control of aconcentration of the mixed product. The controller may be configured tocalculate, or look up in a data store, such as a memory or non-volatiledata store, a parameter dependent on a concentration of the mixedproduct and to employ it as a negative feedback control signal toregulate concentration of said mixed product. Equivalently, the systemis compensating the conduction signal using temperature so that and anconcentration estimate or control signal can be generation.

Referring now to FIGS. 11A through 11C, an active temperature detector800 has two temperature detectors 814, 816, for example resistancetemperature detectors (RTDs) spaced apart along what approximates aone-dimensional thermal flow circuit in the configuration of activetemperature detector 800. The temperature sensor 800 is configured suchthat it can be positioned adjacent the wall of a vessel/channel or fluidchannel (not shown). For example, it may have a flat surface 812 againstwhich the wall of a flexible flat vessel/channel or channel may bepositioned or urged so that a predictable interface without a gap can beprovided. In embodiments, the wall of a flexible channel orvessel/channel is urged by a positive static pressure therein.

The active temperature detector 800 includes a heating/cooling device802 with a side 802B that exchanges heat with a thermal network and aside 802A that exchanges heat with an external medium, such as theambient air. The heating/cooling device 802 may be of any suitableconfiguration as discussed elsewhere in the present application. In theillustrated embodiment, heating/cooling device 802 may be athermoelectric heat pump or simply a dissipative heater. As stated, itcould also be other kinds of suitable devices, for example any that cancontrol the temperature of a side of the thermal network.

RTD-type temperatures detectors 816 and 817 may be spaced apart by anair gap 819. Although RTDs are discussed in the present embodiment, theycould be replaced by any other type of temperature detector such as athermistor, thermocouple, etc. In the present embodiment, a fluid-sideRTD 816 is bonded or soldered to conductive pads on a flexible circuitmember 818. A heating/cooling device-side RTD 816 is bonded or solderedto conductive pads on a flexible circuit member 820. The flexiblecircuit members 818 and 820 may be of any suitable material for carryingthin electrical leads, for example polyimide film used commonly inelectrical systems. The flexible circuit members 818 and 820 materialmay be chosen to provide convenient flexible lead wires for makingelectrical connections. The flexible circuit members 818 and 820 neednot be flexible and in embodiments may be made of rigid materials. Adesirable property of the flexible circuit members 818 and 820 andvariants of them is that their thermal properties do not varysignificantly with mechanical load. Thus, a material whose conductivityand/or diffusivity is constant under various shear and pressureconditions as might attend normal use will provide consistentindications of temperature.

The air gap 817 is established by separating the flexible circuitmembers 818 and 820 by a spacer 808 which has an opening 814 toaccommodate the RTDs 816 and 817. The flexible circuit members 818 and820 may be adhesively bonded to the spacer 808. The spacer may be amonolithic or composite material, for example FR-4 commonly used in theelectrical device industry. A desirable property of the spacer 808 andvariants of it is that the thermal properties do not vary significantlywith mechanical load.

A high thermal conductivity cup 805 has a recess 807 to receive theflexible circuit members 818 and 820 and spacer 808 assembly. The cup805 ensures that a uniform temperature is applied to the non-fluid-sideof the flexible circuit members 818 and 820 spacer 808 assembly by theheating/cooling device 802. For this purpose, the cup 805 may be ofaluminum, copper, gold, or other suitable material. The arrangement,shape, and sizes of the flexible circuit members 818 and 820 spacer 808assembly, including the bodies of the RTDs (which are generally platinumfilms mounted on a substrate) are chosen to ensure that the flow of heatat the center where the RTDs are located is normal to the surface 812.Thus, the spacer 808 should be sufficiently thermally insulating toprovide a required low level of conductive heat transfer in a directionparallel to the surface 812.

Referring now to FIGS. 11D and 11E, the RTDs may be attached to theflexible circuit members 818 and 820 by means of conductive attachmentpoints 906A and 906B, which may be, for example, solder pads. Leads 908may be provided, here defining elongate serpentine paths following apredominately circumferential course to help minimize thermal conductionin a radial direction, which would be diminish the desirable feature ofa substantially one-dimensional thermal network in the regionimmediately around the RTDs. Two pairs of leads 910A, 910B and 912A,912B with respective separate contact pads 916A, 916B and 918A, 918B mayprovide a mechanism for four point resistance measurement, whicheliminates errors due to variations in system lead wire and electricalconnector contact resistance. For example, two of the leads 916A and918A may be used to drive a current and the other two may be connectedto a high impedance voltage measurement device such that any voltagedrop in the high current line will not affect the measurement of voltagedrop across the temperature sensor connected between the pads conductiveattachment points 906A and 906B.

In embodiments, the conductive attachment points 906A and 906B extendaround the opening 814 and are suitably sized and of such material thatthey are sufficiently thermally conductive to ensure that thetemperature across their faces are substantially uniform. This helps toensure a one-dimensional heat transfer network is established, despitethe high thermal resistance of the air gap between the temperaturesensors that may exist. Another aspect of this construction is that thetemperatures sensors (RTDs in this example butt they could be replacedby other types of temperature sensors) 816, 817 can be of a verydifferent thermal conductivity than the spacer 808, without addingcomplexity or manufacturing variability to the feedback controlmechanism upon which active temperature detection is based. Thus, thebodies of the temperature sensors 815, 817, if of highly thermallyconductive material, such as a ceramic, may have a metal resistor (e.g.,platinum) on any part thereof. Since they are positioned in an air gapand attached to the thermally conductive attachment points 906A and906B, their temperatures are those of the attachment points 906A and906B. Thus the thermal gradient is determined by the structure of thespacer 808 and it can be determined that it forms a simple thermalnetwork whose properties are resistant to variability in the size,thermal properties, or other variability in the temperature sensoritself. Further, the manufacturing is simplified because the temperaturesensors 815, 817 can be attached to the flexible circuit members 818 and820 alone. The attachment to the spacer 808 is not a concern formanufacturing, for example as in embodiments in which the temperaturesensors are embedded in the insulating material between them. Inembodiments, an element other than the attachment points may provide fordistributing heat across the spacer 808. For example, thermallyconductive element may be attached to the spacer 808 or the flexiblecircuit elements to distribute heat. Such an element may benon-electrically conductive such as a ceramic.

It will be observed that the flexible circuit members 818 and 820 ofFIGS. 11D and 11E embody a support for a temperature sensor in whichelectrical leads lead from temperature sensor attachment points at acenter of an end portion 909. The following list of characterizations ofthe leads 909 may be implemented in any of the compatible embodimentsdescribed herein and others not specifically described but which may beenabled by the present disclosure. As well, these characterizations maydescribe features that are independent of the others in furtherembodiments.

-   -   In embodiments, the end portion 909 is larger than an elongate        portion 911 of the flexible circuit members 818 and 820.    -   The electrical leads may be arranged in a manner that they take        an indirect path from the end portion 909 to the elongate        portion 911.    -   The indirect path may be such that the leads 908 circumscribe,        at least partly, the attachment points.    -   The indirect path may be such that the leads 908 define        serpentine paths.    -   The indirect path may be such that the major portions of the        leads 908 are curved.    -   The indirect path may be such that the major portions of the        leads 908 follow a path that is substantially tangential to a        circumference of the end portion 909.    -   The indirect path may be such that the major portions of the        leads 908 double back on themselves.

In the embodiment of FIG. 11F, the paths 919 are curved in a singledirection and provide similar benefits to the paths shown in theprevious embodiments for a flexible circuit member 907. Redundant setsof leads 910C, 910D and 912C, 912D and separate contact pads similar to916A, 916B and 918AC, 918B may be provided for four-point resistancemeasurement as discussed above which help to reduce errors due tovariations in lead and/or contact resistance.

Referring now to FIG. 12, an active temperature detector, for exampleone according to the description attending FIG. 11A through 11C, isshown cross section with a heat source/sink 858 having fins 857 and avessel/channel wall 860. Thus FIG. 12 illustrates a complete thermalnetwork as discussed above, connected thermally with the ambient on oneend (heat sink) and with the fluid 870 whose temperature is measure atthe other end. The elements shown in FIG. 12 are labeled using the samenumerals as in FIGS. 11A through 11C so they are not identified again.

FIG. 13 shows a method for verifying thermal contact between an activetemperature detector and a wall of a fluid vessel/channel according toembodiments of the disclosed subject matter. In embodiments, asdescribed with reference to FIG. 5, a vessel/channel 306 is held againstactive temperature detector 314. To confirm contact between the activetemperature detector 314 and the vessel/channel 306, a transient heatpulse is generated in one or more heat sources embedded in, or adjacentto, the active temperature detector 314 surface. The temperatureresponse during heating or the temperature decay attending cooling (orboth) of the relevant portion of the active temperature sensor 314is/are then measured. For example, a time series of temperaturemeasurements can be captured and stored. Preferably the temperature of asurface portion as close as possible to the vessel/channel 306 wall ismeasured. By comparing the thermal response of the measured temperatureto a predicted temperature decay profile. This may be done numericallyor by finding the parameters that best fit a curve, such as anexponential or Gaussian, or straight-line fit to a logarithmic plot to atime series of temperature measurements. Known techniques for measuringconductivity and/or diffusivity can be adapted for determining thequality of the thermal contact so the details are not elaborated here.Uniform and direct contact between the vessel/channel 306 and thesurface of the temperature detector 314 can be distinguished by a purelyempirical approach as well. A slow decay indicates that the thermalcontact between the active temperature detector is poor whilst a rapiddecay indicates good thermal contact. In alternative embodiments, timeseries of temperature measurements are obtained during a heating, or thecombined temperature profile of heating and cooling (recovery) aresampled. Note that the method of FIG. 13 may be practiced apart from theembodiment of FIG. 5. The technique described above can be used inpassive as well as active temperature detectors.

In a system embodiment, a controller may be used to implement the methodof FIG. 13. Referring now to FIG. 13, at S10, a fluid circuit portion ispositioned adjacent the active temperature detector. At S12, a transientthermal pulse is generated. The same device used for measuringtemperature may also be used for measuring temperature. For example, awire or film of an RTD may be used to dissipate thermal energy in thetemperature detector. A suitably designed thermocouple or thermistor maybe used to generate heat as well. In embodiments, a film or wireimmediately adjacent the vessel/channel wall is present in the activetemperature sensor. The transient thermal event may generated by adifferent device from that used to determine temperature. One or moretemperature sensor, heat elements, or combinations thereof may beprovided for this purpose. At S14, a time series of temperatures arerecorded. If multiple sensors are used, then multiple series may besampled and recorded. At S16, the measured time-temperature data arecompared to a predetermined model or template and at S18, adetermination is made whether the data fit a desirable profile or anundesirable profile. If the profile indicates the fit is in a desiredrange, an indication (such as a digital signal) of an acceptableconfiguration is generated at S20, otherwise an indication (such as adigital signal) of an unacceptable configuration is generated. Thesignals may be output to a display, for example, a message to request anoperator to fix the mechanical engagement of the fluid circuit with thevessel/channel with the temperature detector, to replace the fluidcircuit with the vessel/channel, or take some other action.

FIG. 14 shows an active temperature detector with features for verifyingthermal contact between a surface thereof and a wall of a fluidvessel/channel according to embodiments of the disclosed subject matter.A 909 flexible circuit element 950 end portion 951 has an array oftemperature sensors 954 and a center temperature sensor 956 which areall wired to contact pads 964 on a dependent portion 952 thereof. As inearlier-described embodiments, the flexible circuit element may haveonly a single temperature sensor 956. The embodiment illustrated showsmultiple temperature sensors which can verify good thermal contact asdescribed above by energizing each, simultaneously or consecutively acombination thereof and monitoring the transient temperature. Thecircuit leads have various features such as serpentine bends 962 and 958as well as elongate paths that run in generally circumferentialdirections to minimize thermal conduction as discussed above.

Variations of the above embodiments may be formed by providing othershapes of surfaces that define different heat flow paths which may bereliably modeled in order to extrapolate a temperature at a location ofthe heat flow path from two or more temperature measurements. Forexample, an active temperature detector may be configured as acylindrical or spherical heat source with temperature sensors spacedradially apart in a medium whose heat transfer properties can be modeledor are repeatable after calibration.

In any of the above embodiments, a system may be configured to guaranteethat a positive static pressure in a flow channel or vessel/channel withflexible walls is provided. This may ensure good thermal contact betweenthe fluid volume whose temperature is to be measured is consistent withthe model used for extrapolation of the temperature of the fluid. Thesystem may also be provided with a mechanism, such as a stirrer, toensure the fluid temperature is uniform. In addition, in embodiments inwhich there is a fluid that flows through a channel whose temperature isto be measured, the channel may be configured to guarantee that the flowdoes not stagnate whose temperature is uniform across the interfacingsurface of the active temperature detector. This feature may be appliedin any of the embodiments. For this purposes, for example, flow guidesmay help to distribute flow in an expanding section of the fluid circuitto ensure there are no stagnating regions and that all flowcross-sections carry flow. In embodiments, the flow mass rate may beuniform across the region that coincides with the contact surface of theactive temperature detector.

It will be appreciated that the modules, processes, systems, andsections described above can be implemented in hardware, hardwareprogrammed by software, software instruction stored on a non-transitorycomputer-readable medium or a combination of the above. For example, amethod for measuring temperature can be implemented, for example, usinga processor configured to execute a sequence of programmed instructionsstored on a non-transitory computer-readable medium. For example, theprocessor can include, but not be limited to, a personal computer orworkstation or other such computing system that includes a processor,microprocessor, microcontroller device, or is comprised of control logicincluding integrated circuits such as, for example, an ApplicationSpecific Integrated Circuit (ASIC). The instructions can be compiledfrom source code instructions provided in accordance with a programminglanguage such as Java, C++, C#.net or the like. The instructions canalso comprise code and data objects provided in accordance with, forexample, the Visual Basic™ language, LabVIEW, or another structured orobject-oriented programming language. The sequence of programmedinstructions and data associated therewith can be stored in anon-transitory computer-readable medium such as a computer memory orstorage device which may be any suitable memory apparatus, such as, butnot limited to read-only memory (ROM), programmable read-only memory(PROM), electrically erasable programmable read-only memory (EEPROM),random-access memory (RAM), flash memory, disk drive and the like.

Furthermore, the modules, processes, systems, and sections can beimplemented as a single processor or as a distributed processor.Further, it should be appreciated that the steps mentioned above may beperformed on a single or distributed processor (single and/ormulti-core). Also, the processes, modules, and sub-modules described inthe various figures of and for embodiments above may be distributedacross multiple computers or systems or may be co-located in a singleprocessor or system. Exemplary structural embodiment alternativessuitable for implementing the modules, sections, systems, means, orprocesses described herein are provided below.

The modules, processors, or systems described above can be implementedas a programmed general purpose computer, an electronic deviceprogrammed with microcode, a hard-wired analog logic circuit, softwarestored on a computer-readable medium or signal, an optical computingdevice, a networked system of electronic and/or optical devices, aspecial purpose computing device, an integrated circuit device, asemiconductor chip, and a software module or object stored on acomputer-readable medium or signal, for example.

Embodiments of the method and system (or their sub-components ormodules), may be implemented on a general-purpose computer, aspecial-purpose computer, a programmed microprocessor or microcontrollerand peripheral integrated circuit element, an ASIC or other integratedcircuit, a digital signal processor, a hardwired electronic or logiccircuit such as a discrete element circuit, a programmed logic circuitsuch as a programmable logic device (PLD), programmable logic array(PLA), field-programmable gate array (FPGA), programmable array logic(PAL) device, or the like. In general, any process capable ofimplementing the functions or steps described herein can be used toimplement embodiments of the method, system, or a computer programproduct (software program stored on a non-transitory computer-readablemedium).

Furthermore, embodiments of the disclosed method, system, and computerprogram product may be readily implemented, fully or partially, insoftware using, for example, object or object-oriented softwaredevelopment environments that provide portable source code that can beused on a variety of computer platforms. Alternatively, embodiments ofthe disclosed method, system, and computer program product can beimplemented partially or fully in hardware using, for example, standardlogic circuits or a very-large-scale integration (VLSI) design. Otherhardware or software can be used to implement embodiments depending onthe speed and/or efficiency requirements of the systems, the particularfunction, and/or particular software or hardware system, microprocessor,or microcomputer being utilized. Embodiments of the method, system, andcomputer program product can be implemented in hardware and/or softwareusing any known or later developed systems or structures, devices and/orsoftware by those of ordinary skill in the applicable art from thefunction description provided herein and with a general basic knowledgeof heat transfer and/or computer programming arts.

Moreover, embodiments of the disclosed method, system, and computerprogram product can be implemented in software executed on a programmedgeneral purpose computer, a special purpose computer, a microprocessor,or the like.

It is, thus, apparent that there is provided, in accordance with thepresent disclosure, active temperature measurement methods, devices andsystems. Many alternatives, modifications, and variations are enabled bythe present disclosure. Features of the disclosed embodiments can becombined, rearranged, omitted, etc., within the scope of the inventionto produce additional embodiments. Furthermore, certain features maysometimes be used to advantage without a corresponding use of otherfeatures. Accordingly, Applicants intend to embrace all suchalternatives, modifications, equivalents, and variations that are withinthe spirit and scope of the present invention, examples of which aredescribed below.

According to first embodiments, the disclosed subject matter includes avessel/channel with a temperature detecting device. A first temperaturesensor is attached to or placed against a wall of a vessel/channelconfigured for carrying or containing a fluid. A second temperaturesensor is separated from the first temperature sensor by an insulatingbody having a thermal resistance similar to the vessel/channel wall. Atemperature regulating device is in thermal contact with the secondtemperature sensor and configured to receive first and secondtemperature indication signals, respectively, from the first and secondtemperature sensors. The temperature regulating device is furtherconfigured to minimize a difference in temperatures indicated by thefirst and second temperature signals by regulating a rate of flow ofheat between the first and second temperature sensors.

The first embodiments may be revised to form further first embodiments.For example, in such embodiments, the temperature regulating deviceincludes a thermoelectric heat pump. The first embodiments may berevised to form still further first embodiments. For example, in suchembodiments, the temperature regulating device includes a dissipativeheater. The first embodiments may be revised to form still further firstembodiments. For example, in such embodiments, the second temperaturesensor and or the heat controlling device have a surface that extendsbeyond the surface of the first temperature sensor. The firstembodiments may be revised to form still further first embodiments. Forexample, in such embodiments, the insulating body fills the empty spacebetween the second temperature sensor and the fluid vessel/channel wall.The first embodiments may be revised to form still further firstembodiments. For example, in such embodiments, the vessel/channel is abag or flexible membrane configured to contain a medicament, abiological fluid such as blood or plasma, or a fluid circuit configuredto convey a medicament, a biological fluid such as blood or plasma.

According to second embodiments, the disclosed subject matter includes atemperature detecting device with an insulating member with a firstsurface and temperature sensor configured to be attached to or placedagainst a wall of a vessel/channel carrying or containing a fluid, thetemperature sensor being configured to measure a temperature the firstsurface. A heat flux sensor is configured to detect heat flow betweenthe surface and a second surface of the insulating body opposite thefirst surface. A temperature regulating device is in thermal contactwith the second surface. A controller regulates the temperatureregulating device responsively to the heat flux sensor to minimize aflux. The controller is further configured to generate a command tosample temperature measurements when a predefined flux level isdetected.

The second embodiments may be revised to form further secondembodiments. For example, in such embodiments, the temperatureregulating device includes a thermoelectric heat pump. The secondembodiments may be revised to form further second embodiments. Forexample, in such embodiments, the temperature regulating device includesa dissipative heater. The second embodiments may be revised to formfurther second embodiments. For example, in such embodiments, theinsulator member first surface has a major dimension that is larger thana distance between the first and second surfaces. The second embodimentsmay be revised to form further second embodiments. For example, in suchembodiments, the insulating member is of a material with thermalconductivity that is approximately the same as that of the wall.

According to third embodiments, the disclosed subject matter includes asystem for measuring electrical conductivity, a fluid conductionmeasuring circuit, a temperature measuring element, and a controllerconfigured to control the conduction measuring circuit and thetemperature measuring element. The temperature measuring element has atleast one thermal contact portion with a temperature sensor and atemperature measuring circuit and a fluid circuit is configured to carrya fluid, the fluid circuit including a wetted conductor inside aconductivity cell portion, the wetted conductor having a having acontact, external to the fluid circuit, for interfacing with theconduction measuring circuit. The fluid circuit includes at least onetemperature measurement portion having predefined thermal properties andconfigured to touch the thermal contact portion. The controller isconfigured to control the temperature measuring element and theconduction measuring circuit to generate and output at least one set ofcontemporaneous temperature and conduction measurements.

The third embodiments may be revised to form further third embodiments.For example, in such embodiments, the temperature measuring elementincludes an active temperature regulator configured to apply heat to ordraw heat from the contact portion. The third embodiments may be revisedto form further third embodiments. For example, in such embodiments, thetemperature measuring element includes an active temperature regulatorconfigured to apply heat to or draw heat from the contact portion andthe controller is configured to regulate the temperature regulator so asto nullify heat flow through a wall of the temperature measurementportion. The third embodiments may be revised to form further thirdembodiments. For example, in such embodiments, the controller isconfigured to derive a fluid property algorithm or database responsivelyto the contemporaneous temperature and conduction measurements.

According to fourth embodiments, the disclosed subject matter includes amethod for measuring electrical conductivity that includes flowing afluid through a chamber and then over a pair of conductors whileapplying a regulated current between the conductors and measuring avoltage there across to obtain a conductance measurement of the fluid,contacting the chamber with an external temperature measuring device andsampling temperature measurements therefrom, and compensating ornullifying a flow of thermal energy through a wall of the chamber inorder to obtain a temperature measurement estimate of the fluid. Themethod further includes combining the temperature measurement estimateand conductance measurement to estimate a property of the fluid.

According to fifth embodiments, the disclosed subject matter includes atemperature detecting device that includes a first temperature sensorattached to a flat member that is adapted to be placed against a wall ofa vessel/channel configured for carrying or containing a fluid. A secondtemperature sensor is separated from the first temperature sensor by aninsulating gap. A temperature regulating device is in thermal contactwith the second temperature sensor. A controller is configured toreceive first and second temperature indication signals, respectively,from the first and second temperature sensors and to regulate thetemperature regulating device responsively to signals therefrom. Thecontroller is configured to regulate the a heat flux rate through theflat member responsively to the signals from the first and secondtemperature sensors such that a temperature of at least the firsttemperature sensor indicates a temperature of a fluid on an a side ofthe wall opposite the first temperature sensor.

The fifth embodiments may be revised to form further fifth embodiments.For example, in such embodiments, the temperature regulating deviceincludes a thermoelectric heat pump. The fifth embodiments may berevised to form further fifth embodiments. For example, in suchembodiments, the temperature regulating device includes a dissipativeheater. The fifth embodiments may be revised to form further fifthembodiments. For example, in such embodiments, the second temperaturesensor and or the heat controlling device have a surface that extendsbeyond the surface of the first temperature sensor. The fifthembodiments may be revised to form further fifth embodiments. Forexample, in such embodiments, he gap includes an insulating body betweenthe first and second temperature sensors. The fifth embodiments may berevised to form further fifth embodiments. For example, in suchembodiments, the vessel/channel is a bag or flexible membrane configuredto contain a medicament, a biological fluid such as blood or plasma, ora fluid circuit configured to convey a medicament, a biological fluidsuch as blood or plasma. The fifth embodiments may be revised to formfurther fifth embodiments. For example, in such embodiments, a metal orother high thermal conductivity member may be provided adjacent thesecond temperature sensor adapted for maintaining a uniform temperatureacross the temperature regulating device.

According to sixth embodiments, the disclosed subject matter includestemperature detecting device with a first temperature sensor attached toa first flat member that is adapted to be placed against a wall of avessel/channel configured for carrying or containing a fluid and asecond temperature sensor attached to a second flat member separatedfrom the first temperature sensor by a spacer. A temperature regulatingdevice is in thermal contact with the second flat member opposite thesecond temperature sensor. A controller is configured to receive firstand second temperature indication signals, respectively, from the firstand second temperature sensors and to regulate the temperatureregulating device responsively to signals therefrom. The controller isconfigured to regulate the a heat flux rate through the flat memberresponsively to the signals from the first and second temperaturesensors such that a temperature of at least the first temperature sensorindicates a temperature of a fluid on an a side of the wall opposite thefirst temperature sensor.

The sixth embodiments may be revised to form further sixth embodiments.For example, in such embodiments, the temperature regulating deviceincludes a thermoelectric heat pump. The sixth embodiments may berevised to form further sixth embodiments. For example, in suchembodiments, the temperature regulating device includes a dissipativeheater. The sixth embodiments may be revised to form further sixthembodiments. For example, in such embodiments, the second temperaturesensor and or the heat controlling device have a surface that extendsbeyond the surface of the first temperature sensor. The sixthembodiments may be revised to form further sixth embodiments. Forexample, in such embodiments, the gap includes an insulating bodybetween the first and second temperature sensors. The sixth embodimentsmay be revised to form further sixth embodiments. For example, in suchembodiments, the vessel/channel is a bag or flexible membrane configuredto contain a medicament, a biological fluid such as blood or plasma, ora fluid circuit configured to convey a medicament, a biological fluidsuch as blood or plasma. The sixth embodiments may be revised to formfurther sixth embodiments. For example, in such embodiments a highthermal conductivity member may be provided adjacent the secondtemperature sensor adapted for maintaining a uniform temperature acrossthe temperature regulating device. The sixth embodiments may be revisedto form further sixth embodiments. For example, in such embodiments, thefirst and second flat members carry conductors that make electricalcontact between the temperature sensors and the controller. The sixthembodiments may be revised to form further sixth embodiments. Forexample, in such embodiments, the flat members have end portions thatare wider than an elongate portion thereof. The sixth embodiments may berevised to form further sixth embodiments. For example, in suchembodiments, a spacer may be sandwiched between the flat member endportions and effective for spacing the temperature sensors apart. Thesixth embodiments may be revised to form further sixth embodiments. Forexample, in such embodiments, the spacer has an opening in the centerthereof such that an air gap is defined between the temperature sensors.The sixth embodiments may be revised to form further sixth embodiments.For example, in such embodiments, a spacer is sandwiched between theflat members and effective for spacing the temperature sensors apart.The sixth embodiments may be revised to form further sixth embodiments.For example, in such embodiments, the electrical leads are arranged in amanner that they take an indirect path from an end portion of theelongate members whereby thermal conduction from the temperature sensorsin a radial direction is minimized. The sixth embodiments may be revisedto form further sixth embodiments. For example, in such embodiments, theindirect path paths are such that the leads circumscribe, at leastpartly, the temperature sensors. The sixth embodiments may be revised toform further sixth embodiments. For example, in such embodiments, theindirect path paths are such that the leads are serpentine. The sixthembodiments may be revised to form further sixth embodiments. Forexample, in such embodiments, the indirect path paths are curved aroundthe temperature sensors. The sixth embodiments may be revised to formfurther sixth embodiments. For example, in such embodiments, theelectrical leads are arranged in a manner that they take an indirectpath from an end portion of the elongate members whereby thermalconduction from the temperature sensors in a radial direction isminimized. The sixth embodiments may be revised to form further sixthembodiments. For example, in such embodiments, the indirect path pathsare such that the leads circumscribe, at least partly, the temperaturesensors. The sixth embodiments may be revised to form further sixthembodiments. For example, in such embodiments, the indirect path pathsare such that the leads are serpentine. The sixth embodiments may berevised to form further sixth embodiments. For example, in suchembodiments, the indirect path paths are curved around the temperaturesensors. The sixth embodiments may be revised to form further sixthembodiments. For example, in such embodiments, the end portions aresubstantially round and major portions of the leads follow a path thatis substantially tangential to a circumference of the end portions. Thesixth embodiments may be revised to form further sixth embodiments. Forexample, in such embodiments, the indirect path may be such that themajor portions of the leads double back on themselves.

According to seventh embodiments, the disclosed subject matter includesa system for measuring electrical conductivity that has a fluidelectrical resistance measuring circuit, a temperature measuringelement, and a controller configured to control the fluid electricalresistance measuring circuit and the temperature measuring element. Thetemperature measuring element has at least one thermal contact portionwith a temperature sensor and a temperature measuring circuit. A fluidcircuit is configured to carry a fluid, the fluid circuit includescapacitive and/or induction coupling portions to permit resistancemeasurement of a fluid inside a resistivity cell portion, the capacitiveand/or induction coupling portions being connected to a resistancemeasurement circuit for measuring resistance through the capacitiveand/or induction coupling portions, for interfacing with the fluidresistance measuring circuit. The fluid circuit includes at least onetemperature measurement portion has predefined thermal properties andconfigured to touch the thermal contact portion. The controller isconfigured to control the temperature measuring element and the fluidresistance measuring circuit to generate and output at least one set ofcontemporaneous temperature and conduction measurements.

The seventh embodiments may be revised to form further seventhembodiments. For example, in such embodiments, the temperature measuringelement includes an active temperature regulator configured to applyheat to or draw heat from the contact portion. The seventh embodimentsmay be revised to form further seventh embodiments. For example, in suchembodiments, the temperature measuring element includes an activetemperature regulator configured to apply heat to or draw heat from thecontact portion and the controller is configured to regulate thetemperature regulator so as to nullify heat flow through a wall of thetemperature measurement portion. The seventh embodiments may be revisedto form further seventh embodiments. For example, in such embodiments,the controller is configured to derive a fluid property algorithm ordatabase responsively to the contemporaneous temperature and resistancemeasurements.

According to eight embodiments, the disclosed subject matter includes afluid management system with a temperature detecting device. A fluidcircuit has a pump and a controller adapted for controlling the flow offluid in the fluid circuit. A temperature detector is controlled by thecontroller. The temperature detector has a first temperature sensor,attached to or placed against a wall of a portion of the fluid circuitand a second temperature sensor separated from the first temperaturesensor by an insulating body has a thermal resistance similar to theportion wall. A temperature regulating device is in thermal contact withthe second temperature sensor and configured to receive first and secondtemperature indication signals, respectively, from the first and secondtemperature sensors. The temperature regulating device is furtherconfigured to minimize a difference in temperatures indicated by thefirst and second temperature signals by regulating a rate of flow ofheat between the first and second temperature sensors. The controller isfurther configured to control the temperature regulating device toregulate the flow of heat between the first and second temperaturesensors flow of fluid responsively to a signal indicating the presenceof a predetermined minimum flow in the fluid circuit portion.

The eighth embodiments may be revised to form further eighthembodiments. For example, in such embodiments, the temperatureregulating device includes a thermoelectric heat pump. The eighthembodiments may be revised to form further eighth embodiments. Forexample, in such embodiments, the temperature regulating device includesa dissipative heater. The eighth embodiments may be revised to formfurther eighth embodiments. For example, in such embodiments, the secondtemperature sensor and or the temperature regulating device has asurface that extends beyond the surface of the first temperature sensor.The eighth embodiments may be revised to form further eighthembodiments. For example, in such embodiments, the insulating body fillsthe empty space between the second temperature sensor and the fluid wallportion. The eighth embodiments may be revised to form further eighthembodiments. For example, in such embodiments, the wall portion is apart of a bag or flexible membrane configured contain or channel a flowof medicament or a biological fluid such as blood or plasma. The eighthembodiments may be revised to form further eighth embodiments. Forexample, in such embodiments, a thermal conductivity of the insulatingbody is substantially the same as a thermal conductivity of the portionwall. The eighth embodiments may be revised to form further eighthembodiments. For example, in such embodiments, the insulating body hasan air gap in a center thereof and the first and second temperaturesensors are separated across the air gap.

According to ninth embodiments, the disclosed subject matter includes anactive temperature detector with an insulator having at least onetemperature sensor. A heat flux regulation element heats or cools afirst side of the insulator, responsively to one or more firsttemperature sensors, so as to maintain a condition of zero heat fluxunder steady state conditions when a target member is brought intocontact with a second side of the insulator, the second side beingopposite the first side. A controller is configured to generate atransient temperature change in one or more second temperature sensorsand/or the heat flux regulation element and to store temperature samplesindicated by one or more second temperature sensors over a time intervalcoinciding with, or following, the transient temperature change. Thecontroller is further configured to generate a control signal indicatinga characteristic of the thermal contact between the target member andthe insulator responsively to the stored temperature samples.

The ninth embodiments may be revised to form further ninth embodiments.For example, in such embodiments, the target member is a portion of afluid circuit. The ninth embodiments may be revised to form furtherninth embodiments. For example, in such embodiments, the target memberis a portion of a fluid-containing vessel or channel. The ninthembodiments may be revised to form further ninth embodiments. Forexample, in such embodiments, the target member is a portion of a fluidcircuit of a medical treatment device. The ninth embodiments may berevised to form further ninth embodiments. For example, in suchembodiments, the target member is a flexible panel of a fluid circuit ofa medical treatment device. The ninth embodiments may be revised to formfurther ninth embodiments. For example, in such embodiments, the heatflux regulation element includes a thermoelectric heating/coolingdevice. The ninth embodiments may be revised to form further ninthembodiments. For example, in such embodiments, the heat flux regulationelement includes a dissipative heater. The ninth embodiments may berevised to form further ninth embodiments. For example, in suchembodiments, the at least one temperature sensor includes at least twotemperature sensors. The ninth embodiments may be revised to formfurther ninth embodiments. For example, in such embodiments, the firstone or more temperature sensors are the same as the second one or moretemperature sensors. The ninth embodiments may be revised to formfurther ninth embodiments. For example, in such embodiments, the firstone or more temperature sensors are different from the second one ormore temperature sensors. The ninth embodiments may be revised to formfurther ninth embodiments. For example, in such embodiments, the firstone or more temperature sensors includes at least two temperaturesensors and one of them is the second one or more temperature sensors.The ninth embodiments may be revised to form further ninth embodiments.For example, in such embodiments, the control signal is output to a userinterface adapted to indicate the characteristic. The ninth embodimentsmay be revised to form further ninth embodiments. For example, in suchembodiments, the characteristic indicates whether there is an air gapbetween the insulator and the target member. The ninth embodiments maybe revised to form further ninth embodiments. For example, in suchembodiments, the controller is configured to generate the transienttemperature change by driving a current through one of the one or moresecond temperature sensors.

According to tenth embodiments, the disclosed subject matter includes anactive temperature detector with an insulator with at least onetemperature sensor. A heat flux regulation element that heats or cools afirst side of the insulator, responsively to temperature sensorsattached to the insulator, so as to maintain a condition of zero heatflux under steady state conditions when a target member is brought intocontact with a second side of the insulator, the second side beingopposite the first side. A controller is configured to generate atransient temperature change by driving a current through one of thetemperature sensors or the heat flux regulation element and to storetemperature samples indicated by one of the temperature sensors over atime interval coinciding with, or following, the transient temperaturechange. The controller is further configured to generate a controlsignal indicating a characteristic of the thermal contact between thetarget member and the insulator responsively to the stored temperaturesamples.

The tenth embodiments may be revised to form further tenth embodiments.For example, in such embodiments, the target member is a portion of afluid circuit of a medical treatment device. The tenth embodiments maybe revised to form further tenth embodiments. For example, in suchembodiments, the target member is a portion of a fluid circuit. Thetenth embodiments may be revised to form further tenth embodiments. Forexample, in such embodiments, the target member is a portion of afluid-containing vessel or channel. The tenth embodiments may be revisedto form further tenth embodiments.

For example, in such embodiments, the target member is a portion of afluid circuit of a medical treatment device. The tenth embodiments maybe revised to form further tenth embodiments. For example, in suchembodiments, the target member is a flexible panel of a fluid circuit ofa medical treatment device. The tenth embodiments may be revised to formfurther tenth embodiments. For example, in such embodiments, the heatflux regulation element includes a thermoelectric heating/coolingdevice. The tenth embodiments may be revised to form further tenthembodiments. For example, in such embodiments, the heat flux regulationelement includes a dissipative heater. The tenth embodiments may berevised to form further tenth embodiments. For example, in suchembodiments, the control signal is output to a user interface adapted toindicate the characteristic. The tenth embodiments may be revised toform further tenth embodiments. For example, in such embodiments, thecharacteristic indicates whether there is an air gap between theinsulator and the target member. The tenth embodiments may be revised toform further tenth embodiments. For example, in such embodiments, thecontroller is configured to generate the transient temperature change bydriving a current through one of the one or more second temperaturesensors.

According to eleventh embodiments, disclosed subject matter includes atemperature detecting device with a first temperature sensor attached toan interface member that is adapted to be placed against a wall of avessel/channel configured for carrying or containing a fluid. A secondtemperature sensor is separated from the first temperature sensor by aninsulating gap. A temperature regulating device in thermal contact withinterface member and closer to the second temperature sensor then thefirst temperature sensor. A controller is configured to receive firstand second temperature indication signals, respectively, from the firstand second temperature sensors and to regulate the temperatureregulating device responsively to signals therefrom. The controller isconfigured to regulate a heat flux rate through the interface memberresponsively to the signals from the first and second temperaturesensors such that a temperature of at least the first temperature sensorindicates a temperature of a fluid on an a side of the wall opposite thefirst temperature sensor.

The eleventh embodiments may be revised to form further eleventhembodiments. For example, in such embodiments, the temperatureregulating device includes a thermoelectric heat pump. The eleventhembodiments may be revised to form further eleventh embodiments. Forexample, in such embodiments, the temperature regulating device includesa dissipative heater. The eleventh embodiments may be revised to formfurther eleventh embodiments. For example, in such embodiments, thesecond temperature sensor and or the heat controlling device have asurface that extends beyond the surface of the first temperature sensor.The eleventh embodiments may be revised to form further eleventhembodiments. For example, in such embodiments, the gap includes aninsulating body between the first and second temperature sensors. Theeleventh embodiments may be revised to form further eleventhembodiments. For example, in such embodiments, the vessel/channel is abag or flexible membrane configured to contain a medicament, abiological fluid such as blood or plasma, or a fluid circuit configuredto convey a medicament, a biological fluid such as blood or plasma. Theeleventh embodiments may be revised to form further eleventhembodiments. For example, in such embodiments, a metal member isadjacent the second temperature sensor adapted for maintaining a uniformtemperature across the temperature regulating device. The eleventhembodiments may be revised to form further eleventh embodiments. Forexample, in such embodiments, the gap includes an air gap between thefirst and second temperature sensors. The eleventh embodiments may berevised to form further eleventh embodiments. For example, in suchembodiments, the interface member has a surface that is of acomplementary shape to a surface of the wall effective to ensure uniformthermal resistance over an interfacing area therebetween. The eleventhembodiments may be revised to form further eleventh embodiments. Forexample, in such embodiments, the wall is flexible and the interfacemember has a smooth surface to which the wall is conformable such that athermal resistance over an interfacing area therebetween is uniform. Theeleventh embodiments may be revised to form further eleventhembodiments. For example, in such embodiments, the wall is one ofconcave and convex and the interface member has an interfacing surfacethat interfaces with the wall that is the other of concave and convex,such that a thermal resistance over an interfacing area therebetween isuniform. The eleventh embodiments may be revised to form furthereleventh embodiments. For example, in such embodiments, the interfacemember has an identical shape to a surface of the wall effective toensure uniform thermal resistance over an interfacing area therebetween.The eleventh embodiments may be revised to form further eleventhembodiments. For example, in such embodiments, the wall of avessel/channel is a part of a fluid circuit of a medical treatmentdevice.

According to twelfth embodiments, the disclosed subject matter includesa temperature detecting device with a first temperature sensor attachedto a first flat member that is adapted to be placed against a wall of avessel/channel configured for carrying or containing a fluid. A secondtemperature sensor is attached to a second flat member separated fromthe first temperature sensor by a spacer. The spacer has openings in acenter thereof in which the first and second temperature sensors arereceived. The first and second flat members being attached to the spacersuch that the first and second temperature sensors are attachedindirectly through the first and second flat member, respectively, tothe spacer.

The twelfth embodiments may be revised to form further twelfthembodiments. For example, in such embodiments, an air gap separates thefirst and second sensors. The twelfth embodiments may be revised to formfurther twelfth embodiments. For example, in such embodiments, thespacer and temperature sensors are not directly attached. The twelfthembodiments may be revised to form further twelfth embodiments. Forexample, in such embodiments, the first and second flat members arebonded to the spacer. The twelfth embodiments may be revised to formfurther twelfth embodiments. For example, in such embodiments, atemperature regulating device is in thermal contact with the second flatmember opposite the second temperature sensor; a controller configuredto receive first and second temperature indication signals,respectively, from the first and second temperature sensors and toregulate the temperature regulating device responsively to signalstherefrom; the controller being configured to regulate the a heat fluxrate through the flat member responsively to the signals from the firstand second temperature sensors such that a temperature of at least thefirst temperature sensor indicates a temperature of a fluid on an a sideof the wall opposite the first temperature sensor. The twelfthembodiments may be revised to form further twelfth embodiments. Forexample, in such embodiments, the temperature regulating device includesa thermoelectric heat pump or a dissipative heater. The twelfthembodiments may be revised to form further twelfth embodiments. Forexample, in such embodiments, the spacer and first and second flatmembers are adhesively or thermally bonded together. The twelfthembodiments may be revised to form further twelfth embodiments. Forexample, in such embodiments, the second temperature sensor and or theheat controlling device have a surface that extends beyond the surfaceof the first temperature sensor. The twelfth embodiments may be revisedto form further twelfth embodiments. For example, in such embodiments,the vessel/channel is a bag or flexible membrane configured to contain amedicament, a biological fluid such as blood or plasma, or a fluidcircuit configured to convey a medicament, a biological fluid such asblood or plasma. The twelfth embodiments may be revised to form furthertwelfth embodiments. For example, in such embodiments, a metal heattransfer member of Aluminum Nitride, Beryllium Oxide is adjacent thesecond temperature sensor adapted for maintaining a uniform temperatureacross the temperature regulating device. The twelfth embodiments may berevised to form further twelfth embodiments. For example, in suchembodiments, the first and second flat members carry conductors thatmake electrical contact between the temperature sensors and thecontroller. The twelfth embodiments may be revised to form furthertwelfth embodiments. For example, in such embodiments, the flat membershave end portions that are wider than an elongate portion thereof. Thetwelfth embodiments may be revised to form further twelfth embodiments.For example, in such embodiments, the spacer has an opening in thecenter thereof such that an air gap is defined between the temperaturesensors. The twelfth embodiments may be revised to form further twelfthembodiments. For example, in such embodiments, the first and second flatmembers have electrical leads arranged in a manner that they take anindirect path from an end portion of the elongate members wherebythermal conduction from the temperature sensors in a radial direction isminimized. The twelfth embodiments may be revised to form furthertwelfth embodiments. For example, in such embodiments, the indirect pathpaths are such that the leads circumscribe, at least partly, thetemperature sensors. The twelfth embodiments may be revised to formfurther twelfth embodiments. For example, in such embodiments, theindirect path paths are such that the leads are serpentine. The twelfthembodiments may be revised to form further twelfth embodiments. Forexample, in such embodiments, the indirect path paths are curved aroundthe temperature sensors. The twelfth embodiments may be revised to formfurther twelfth embodiments. For example, in such embodiments, the firstand second flat members have electrical leads arranged in a manner thatthey take an indirect path from an end portion of the elongate memberswhereby thermal conduction from the temperature sensors in a radialdirection is minimized. The twelfth embodiments may be revised to formfurther twelfth embodiments. For example, in such embodiments, theindirect path paths are such that the leads circumscribe, at leastpartly, the temperature sensors. The twelfth embodiments may be revisedto form further twelfth embodiments. For example, in such embodiments,the indirect path paths are such that the leads are serpentine. Thetwelfth embodiments may be revised to form further twelfth embodiments.For example, in such embodiments, the indirect path paths are curvedaround the temperature sensors. The twelfth embodiments may be revisedto form further twelfth embodiments. For example, in such embodiments,the end portions are substantially round and major portions of the leadsfollow a path that is substantially tangential to a circumference of theend portions. The twelfth embodiments may be revised to form furthertwelfth embodiments. For example, in such embodiments, the indirect pathmay be such that the major portions of the leads double back onthemselves. The twelfth embodiments may be revised to form furthertwelfth embodiments. For example, in such embodiments, the heat transfermember includes one or both of Aluminum Nitride and Beryllium Oxide.

It will be apparent to those of skill in the art that a feature of theactive temperature detector embodiments disclosed above is an insulatorwith at least one temperature sensor, a heat flux regulation elementthat heats or cools a first side of said insulator, responsively to theat least one temperature sensor, so as to maintain a condition of zeroheat flux under steady state conditions when a target member, such as afluid channel or vessel, is brought into contact with a second side ofsaid insulator where the second side being opposite said first side.

1. A vessel/channel with a temperature detecting device, comprising: afirst temperature sensor attached to or placed against a wail of avessel/channel configured for carrying or containing a fluid; a secondtemperature sensor separated from the first temperature sensor by aninsulating body having a thermal resistance similar to thevessel/channel wall; a temperature regulating device in thermal contactwith the second temperature sensor and configured to receive first andsecond temperature indication signals, respectively, from the first andsecond temperature sensors; the temperature regulating device beingfurther configured to minimize a difference in temperatures indicated bysaid first and second temperature signals by regulating a rate of flowof heat between the first and second temperature sensors.
 2. The deviceof claim 1, wherein the temperature regulating device includes athermoelectric heat pump or a dissipative heater.
 3. (canceled)
 4. Thedevice of claim 1, wherein at least one of the second temperature sensorand the temperature regulating device has a surface that extends beyonda surface of the first temperature sensor.
 5. The device of claim 1,wherein the insulating body fills an empty space between the secondtemperature sensor and the fluid vessel/channel wall.
 6. The device ofclaim 1, wherein the vessel/channel is a bag or flexible membraneconfigured to contain a medicament or a biological fluid or thevessel/channel is a fluid circuit configured to convey a medicament or abiological fluid. 7-16. (canceled)
 17. A temperature detecting device,comprising: a first temperature sensor attached to a flat member that isadapted to be placed against a wall of a vessel/channel configured forcarrying or containing a fluid; a second temperature sensor separatedfrom the first temperature sensor by an insulating gap; a temperatureregulating device in thermal contact with the second temperature sensor;and a controller configured to receive first and second temperatureindication signals, respectively, from the first and second temperaturesensors and to regulate said temperature regulating device responsivelyto the temperature indication signals therefrom; the controller beingconfigured to regulate a heat flux rate through said flat memberresponsively to said temperature indication signals from said first andsecond temperature sensors such that a temperature of at least saidfirst temperature sensor indicates a temperature of a fluid on an a sideof said wall opposite said first temperature sensor.
 18. The device ofclaim 17, wherein the temperature regulating device includes athermoelectric heat pump.
 19. The device of claim 17, wherein thetemperature regulating device includes a dissipative heater.
 20. Thedevice of claim 17, wherein at least one of the second temperaturesensor and or the temperature regulating device has a surface thatextends beyond a surface of the first temperature sensor.
 21. The deviceof any of claim 17, wherein the insulating gap includes an insulatingbody between the first and second temperature sensors.
 22. The device ofclaim 17, wherein the vessel/channel is a bag or flexible membraneconfigured to contain a medicament or a biological fluid, or thevessel/channel is a fluid circuit configured to convey a medicament or abiological fluid.
 23. (canceled)
 24. A temperature detecting device,comprising: a first temperature sensor attached to a first flat memberthat is adapted to be placed against a wall of a vessel/channelconfigured for carrying or containing a fluid; a second temperaturesensor attached to a second flat member separated from the firsttemperature sensor by a spacer; a temperature regulating device inthermal contact with the second flat member opposite the secondtemperature sensor; and a controller configured to receive first andsecond temperature indication signals, respectively, from the first andsecond temperature sensors and to regulate said temperature regulatingdevice responsively to the temperature indication signals therefrom: thecontroller being configured to regulate a heat flux rate through saidfirst flat member or said second flat member responsively to saidtemperature indication signals from said first and second temperaturesensors such that temperature of at least said first temperature sensorindicates a temperature of a fluid on an a side of said wall oppositesaid first temperature sensor.
 25. The device of claim 24, wherein thetemperature regulating device includes a thermoelectric heat pump or adissipative heater.
 26. The device of claim 24, wherein the spacer andfirst and second flat members are adhesively or thermally bondedtogether. 27-29. (canceled)
 30. The device of claim 24, furthercomprising a heat transfer member of Aluminum Nitride, or BerylliumOxide, the heat transfer member being disposed adjacent said secondtemperature sensor and adapted for maintaining a uniform temperatureacross the temperature regulating device.
 31. The device of claim 24,wherein the first and second flat members carry conductors that makeelectrical contact between the temperature sensors and the controller.32. The device of claim 24, further comprising a heat transfer member ofmetal or ceramic adjacent said second temperature sensor and adapted formaintaining a uniform temperature across the temperature regulatingdevice.
 33. The device of claim 24, further comprising thermallyconductive attachment portions on one, both of, or between the spacerand the first and second flat members, adapted to distribute heat indirections forming a right angle to the line between the first andsecond temperature sensors.
 34. The device of claim 24, wherein thespacer has an opening in the center thereof such that an air gap isdefined between the first and second temperature sensors. 35-36.(canceled)
 37. The device of claim 31, wherein the first and second flatmembers have electrical leads arranged in a manner such that eachelectrical lead follows a indirect path from an end portion of one ofthe first and second flat members, whereby thermal conduction from thefirst and second temperature sensors in a radial direction is minimized.38. The device of claim 37, wherein the indirect paths are such that theelectrical leads circumscribe, at least partly, the first and secondtemperature sensors.
 39. The device of claim 37, wherein the indirectpaths are such that the electrical leads are serpentine.
 40. The deviceof claim 37, wherein the indirect paths are such that the electricalleads curve around the first and second temperature sensors. 41-44.(canceled)
 45. The device of claim 37, wherein each said end portion issubstantially round and major portions of the electrical leads follow arespective path that is substantially tangential to a circumference ofone of the end portions.
 46. The device of claim 45, wherein theindirect paths are such that the major portions of the electrical leadsdouble back on themselves. 47-122. (canceled)